1. Field of the Invention
This invention relates to temporary barriers which delay the contact of one reactant with another reactant in photographic elements and more particularly to color diffusion transfer film units wherein one portion of the color unit is temporarily isolated from another portion by a barrier layer comprising a mixture of about 30 to 97 weight percent of polymerized N-alkyl-substituted acrylamide, about 3 to 25 weight percent polymerized crosslinking monomer having at least two addition polymerizable groups per molecule, and 0 to 60 weight percent of one or more other polymerized monomers, these polymers having a solubility parameter .delta. from about 13 to 16 at 25.degree. C. with the proviso that the other monomers comprise less than 5 weight percent of cationic monomers, less than 15 weight percent of free acid monomers, and less than 3 weight percent of metal or ammonium salts of acid monomers.